The Influence of Exchangeable Sodium Percentage on Soil Erodibility1
- Michael J. Singer,
- Peter Janitzky and
- John Blackard2
Three experiments were run to determine the effect of exchangeable sodium percentage (ESP) on soil erodibility. In experiment 1, three samples of Colusa silt loam with ESPs of 4, 54, and 73 were eroded with a small laboratory rainfall simulator. Soil loss from the ESP = 4 sample was 20 % less than from the ESP = 54 sample, and 24 % less than the ESP = 73 sample. For experiment 2, Pescadero and Sacramento A horizons were eroded at their natural ESPs (15 and 4, respectively), at 100 % calcium (Ca) or magnesium (Mg) saturation for Pescadero, and 100 % sodium (Na) or Mg saturation for Sacramento. The Ca- or Mg-saturated Pescadero samples eroded at the same rate which was one-third the erodibility of the natural Pescadero. The natural and Mg-saturated Sacramento samples eroded at the same rate which was one-third the erodibility of the ESP = 100 Sacramento samples. These two experiments indicate the importance of Na in increasing erodibility. In experiment 3, Contra Costa silty clay loam and Hillgate loam were eroded at ESPs ranging from 0 to 81. Increasing the ESP from 0 to 2 nearly doubled the soil detachment from the Contra Costa sample. Soil detachment increased significantly up to ESP = 12 and then remained steady to ESP = 80. Hillgate's soil detachability increased significantly from ESP 0 to 2. Further increases in ESP did not increase soil detachment significantly. Clay content and exchange capacity appear to be important factors causing differences in behavior of the two soils.
Nomograph K values for soils with ESP > 2 should be increased to account for the effect of Na. Data for the Colusa silt loam indicate that a 20% increase in K value may be appropriate.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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